Sandwich panels consist of a lightweight core and a face layer or sheet secured to each side of the core or to only one side thereof (so called semi-sandwich panels) and are well known within many technical fields. Such panels are generally used mainly for their excellent strength and stiffness in relation to the low overall weight and in certain designs also for the very good shock-absorbing qualities. The low weight is obtained by means of the low density of especially the core material that may consist of multiple closed cells containing air or other material.
The most common materials used for the face layers are metal, plastic or fiber composite. The core material is usually produced of metal or other non organic low density material forming small or big regular or irregular cells. In cases where the different metal and/or other non-organic layers are pre-manufactured from material hardened prior to their assembly there is traditionally only one way of producing the sandwich structure or panel, and that is to glue the layers together. Such sandwich panels in which organic materials, polymer materials or other synthetic materials are used as adhesive between the layers, of e.g. metal, are restricted in their fields of application. In particular, they will in most cases not withstand aggressive chemicals or high temperatures very well.
However, sandwich materials containing only synthetic material have lately become more frequent. The manufacturing processes used to produce many of such commonly employed sandwich panels consisting of synthetic material in both surface layers and in the core, especially composite sandwich panels, are still mostly manual and thereby rather expensive. The sizes of such sandwich structures/panels that can be practically produced are mainly restricted to the sizes of autoclaves that are conventionally used for pressing the layers together and for hardening the panels.